Apparatus for coupling ultra high frequency systems



June 19, 1951 M. D. FISKE 2557,180

APPARATUS FOR COUPLING ULTRA HIGH FREQUENCY SYSTEMS Filed April 2'7, 1943 Fig.1. 3 H M it E P i v 6 a m Live Fig.3.

If 9- l3 E u w .lzf E g Inventor:

Mi lan D. Fiske,

His Attorney.

Patented June 19, 1951 APPARATUS FOR COUPLING ULTRA HIGH FREQUENCY SYSTEMS MilanD. Fiske, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application April 27, 1943, Serial No. 484,736

3 Claims. 1

My invention relates to apparatus and methods for coupling ultra high frequency systems, and more particularly to apparatus and methods for coupling dielectric wave guides of the hollowpipe type, concentric or coaxial transmission lines, or interconnecting wave guides and coaxial transmission lines.

It is an object of my invention to provide a new and improved coupling device for ultra high frequency systems.

It is another object of my invention to provide new and improved methods of coupling elements or parts of ultra high frequency systems applicable to the field of microwave transmission.

It is a further object of my invention to provide a new and improved device for coupling a dielectric wave guide of the hollow-pipe type to a coaxial or concentric transmission line.

It is a still further object of my invention to provide a new and improved coupling means for interconnecting dielectric wave guide sections or concentric transmission lines.

It is a still further object of my invention to provide a new and improved apparatus and method for coupling or tuning elements or parts of ultra high frequency systems.

It is a still further object of my invention to provide a new and improved device whereby the coupling effect between elements of an ultra high frequency system may be readily controlled.

Briefly stated, in accordance with a general aspect of my invention, I provide new and improved apparatus and methods for coupling elements or parts of high frequency systems, such as systems designed for the utilization of ultra high frequency electromagnetic waves or microwaves. A confined or localized region of charged electrical particles is employed as a coupling element or electrode, the density of which may be controlled to establish or control the coupling between elements or parts of the high frequency system. Where a high coupling coefficient is desired, the density of the particles comprising the discharge is controlled so that in eiiect the dis charge path acts as a conductor, serving as an element or electrode for the interconnection of related parts of the system. By controlling the electric discharge path, this method may be employed to accomplish a variety of results. Some of the uses to which this method may be put are the provision of a continuously variable attenuator, a simple on-oif control of the coupling between elements or units, or a controllable tuning element.

The above described discharge path may be furnished by an electric discharge device, either of the high vacuum type or of the type employing an ionizable medium, and in which a dielec tric evacuated envelope encloses a plurality of electrodes between which the electric discharge is established or provided.

In-accordance with a still further feature of my invention, the discharge device may be of peculiar configuration to accomplish the above described coupling effect, while minimizing reflections of electromagnetic waves due to interconnection of the system parts. For example, where the coupling device which I provide isemployed for the interconnection of a concentric or coaxial transmission line and a dielectric wave guide, the enclosing envelope is preferably of relatively small longitudinal cross sectional area relative to the transverse cross sectional area of the guide. The enclosing envelope may be adapted to be inserted within an outer conductor of a concentric transmission line and provided with an electrode, or electrodes, at each end thereof to permit ready connection to an inner conductor of a coaxial transmission line. This feature of construction may also be employed as a variable coupling device between two concentric or coaxial transmission line sections.

For a better understanding of my invention, reference may be had to the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims. Fig. 1 illustrates an embodiment of my invention as applied to a system for coupling a dielectric wave guide of the hollowpipe type and a concentric transmission line, and Fig. 2 is a transverse cross sectional view of the guide showing the position of the coupling de vice therein. Fig. 3 is another modification ofv my invention showing an arrangement for coupling a pair of dielectric wave guides of the hollow-pipe type. Fig. 4 shows the manner in which my invention may be applied to a system for controlling the coupling between two concentric transmission lines.

Referring now more particularly to Fig. l, I have there illustrated my invention as applied to an ultra high frequency system peculiarly adapted for transmitting microwaves and which may comprise a dielectric wave guide of the hollow-pipe type defined by a conductive or.

metallic member I defining therein a region through which the electromagnetic waves are propagated dielectrically. While it is to be appreciated that my invention is applicable to systems for controlling the propagation of electromagnetic waves of either the transverse electric or the transverse magnetic type, I have chosen to represent my invention as applied to a system where H01 type waves may be utilized. A concentric or coaxial transmission line comprising an outer conductor 2, preferably metallic in nature, and an inner conductor 3 are connected to the dielectric wave guide through the coupling. device explained immediately hereinafter, andmay be connected to other elements of a high frequency system (not illustrated). Conductors 2 and 3 are separated and maintained in spaced relation by means of a tubular insulator i, and the outer conductor 2 is preferably arranged to provide therein a recess to receive one end of a coupling device described immediately hereinafter.

The coupling device which I provide comprises means, such as an elect 'ic discharge device, for establishing within the region defined by meinber I a confined or localized region of charged electrical particles, such as electrons or ions, which controls the coupling effect or the coefficient of coupling between the wave guide and the coaxial transmission line. This means may cornprise an electric discharge device 5 including a dielectric or vitreous envelope i1, preferably of elongated. tubular form and supporting a plurality of electrodes, such as a pair of electrodes l and 8, between which an electric discharge is established. The longitudinal cross sectional area of the electric discharge device 5 with respect to the transverse cross sectional area of the dielectric wave guide is relatively small as illustrated in Fig. 2 which is a partial transverse cross sectional view of the guide and the transmission line.

Either, or both, or the electrodes l and 8 of the discharge device 5 may be adapted to facilitate connection to an external conductor, such as the inner conductor, of a coaxial transmission line, in which case the electrodes, such as electrode I, constitute a part of the end of the discharge device having an externally accessible area which is placed in juxtaposition to the conductor with which it is desired to make connection. It will be noted that electrode '5 immediately engages inner conductor 3 of the transmission line and, as illustrated, may be provided with a contrally positioned cylindrical protuberance 9 which is inserted within a recess provided by inner conductor 3.

So that the connection between the coupling device and a concentric transmission line may be continuous, the transverse dimensions or diameters of the electrode 7 and the envelope E may be made substantially equal to the diameters of inner conductor 3 and tubular insulator respectively, so that the interconnection of the coupling device to the line presents substantially no discontinuities, thereby minimizing reflection oi electromagnetic waves.

The discharge device 5, and particularly the enclosing envelope 6, may be of sufficient length to extend through the dielectric wave guide and having one extremity thereof supported by a cylindrical cup it comprising a part of member I. Furthermore, in order to minimize discontinuities offered to the transmission of electromagnetic waves within the guide, the electrodes, such as electrode 8, may be positioned so that the upper surface H is in the same plane with the bottom inner surface of the member i which defines the region through which the waves are propagated.

In accordance with one aspect of my invention, I contemplate the provision oi a coupling means, such as a column or region or" charged electrical particles, either electrons or ions, the density of which may be suihcient so that the discharge path or the electric column serves as a conductor to eiiect coupling between the parts of the high frequency system. In accordance with a further feature, I contemplate the pro vision of an electric discharge path of centroilable density to control the coupling effect or the coefficient of coupling between such parts. For example, the discharge device 5 may include an ionizable medium and the electrodes '5 and 8 of discharge device 5 may be energized from a controllable source of voltage or current, such as a battery E2, the magnitude of the voltage impressed across the electrodes determining the density of the charged electrical particles within envelope 8. I have found that the coupling efiect between the coaxial transmission line and the dielectric medium of the wave guide is a function of the density of the charged electrical particles, the coupling effect increasing as the density increases. An arrangement such as that shown in Fig. 1 may be employed as a simple on-off coupling control, in which instance a suitable circuit controlling means, such as a switch i3, may be interposed between the battery i2 and the coupling device, the coupling being substantially zero in the absence of an electric discharge.

Upon the establishment of an electromagnetic wave ithin the wave guide having a direction of propagation indicated, for example, by the arrow H01, the electric component of the incident electromagnetic field will be substantially perpendicular to the direction of wave propagation as indicated by the arrow E. Without entering into an extended discussion of the mechanism by virtue of which the coupling is effected between the wave guide and the concentric transmission line, it may be stated that the region of charged electrical particles serves as a wave coupling element between the wave guide and the inner conductor 3 and the outer tubular conductor 2 of the transmission line. I have found that the degree or coefficient of coupling increases as the density of the charged particles increases. Coupling arrangements such as that shown in Fig. 1 may be employed for tuning an element, or elements, of an ultra high frequency system. In this manner, the electric discharge device 5 comprises an electrically controlled, continuously variable tuning element. In addition, by com trolling the density of the discharge within device 5, the device may be employed as a continuously variable attenuator for a dielectric wave guide. A still further application would be the utilization of such an arrangement for bleeding or deriving energy from a dielectric Wave guide,

' the sink (not shown) being connected to the concentric transmission line.

Fig. 3 diagrammatically illustrates another arrangement to which my invention may be applied, that is, for coupling a pair 01' dielectric Wave guides It and it which may be overlapping having a common boundary iii. The coupling de vice may be of a configuration and form generally shown in Fig. l and may include an electric discharge device ll comprising an elongated vitreous or dielectric envelope I8 having therein a pair of electrodes i9 and 20 between which an electric discharge is established. The electrodes [9 and 2B may be positioned so that the surfaces thereof lie in substantially the same plane with the associated members defining the wave guide, thereby minimizing reflections of the electromagnetic waves which are to be controlled.

The system of Fig. 3 operates in substantially the same way as that explained above in connection with Fig. l, the degree of coupling or the coefficient of coupling between dielectric wave guides us and I5 being a function of the density of the electric discharge established between electrodes i9 and 28.

A still further modification of my invention is illustrated in Fig. 4 wherein a pair of concentric or coaxial transmission line sections 2| and 22 are interconnected through a coupling device. The transmission line sections 2| and 22 may include a common outer tubular conductor 23 and may include inner conductors 24, 25 and tubular insulators 26 and 21, respectively.

The coupling device which I provide in this connection is also of the continuously variable type wherein the coupling eifect or coefficient of coupling between the concentric transmission line sections 2| and 22 is obtained by establishing a controllable electric discharge path between the respective sections. The controllable discharge path may be provided by an electric discharge device including a tubular dielectric or vitreous member 28 supporting a pair of spaced electrodes 29 and 30 which may comprise part of the end sealing structures for the device as a whole, which is in end-to-end contact with the transmission line sections. In such an arrangement, the electrodes 29 and 30 may be of cylindrical cross section being sealed to the vitreous member 28. Furthermore, electrodes 29 and 30 may be provided with cylindrical extensions 3| and 32 which are inserted within appropriately formed recesses in the ends of inner conductors 24 and 25. The coupling between transmission line sections 2| and 22 is increased as the density of the charged electrical particles is increased. In this manner the energy flow between the two sections of the transmission line may be controlled completely throughout a predetermined range, or the coupling between the sections may be reduced to substantially zero by extinguishing the electric discharge between the electrodes 29 and 30 by decreasing the voltage applied to the electrodes, such as that effected by opening switch l3.

It will be apparent that I may employ in systems such as shown in Figs. 1, 3 and 4 an electric discharge device wherein the initiation of current flow between the electrodes or the value of the current which flows is controlled by means of interspaced control members, such as electrostatic control grids, in which instance the density of the charged electrical particles may be determined or controlled by the potential impressed on such grids, thereby controlling the coupling between the various parts of the high frequency systems. Certain features of the invention described above are claimed in my co-pending divisional application, Serial No. 134,789, filed December 23, 1949.

The electric discharge devices comprising elements of the coupling devices described above in connection with several embodiments of my invention may be either of the high vacuum type or of the type employing an ionizable medium, such as a gas or a vapor. In such instances, the electric discharge devices may employ a thermionic cathode which comprises one element or electrode of the devices. Alternatively, the electric discharge devices may be of the type comprising a hot or thermionic cathode in conjunction with another electrode serving as an anode or in combination with an anode and a single or a plurality of control electrodes, such as electrostatic control grids.

While I have shown my invention as applied to ultra high frequency systems including specific parts or elements and as employing an electric discharge device of particular form, it will be obvious to those skilled in the art that changes and modifications may be made without departing from my invention, and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a coupling system the combination comprising two concentric transmission line sections each including an inner conductor and an outer tubular conductor separated by a tubular insulator, an evacuated tubular member connected between said sections and containing a pair of axially displaced electrodes for establishing an electrical discharge therebetween which serves as a coupling element, the dimensions of said electrodes being substantially equal to the dimensions of said inner conductors.

2. In a coupling system the combination comprising two concentric transmission line sections having a common outer tubular conductor and. separate inner conductors each separated from the outer conductor by a tubular insulator, an evacuated dielectric tubular member containing a pair of axially displaced electrodes for establishing an electric discharge therebetween which serves as a coupling element between the transmission line sections, said electrodes being electrically connected to and having transverse dimensions substantially equal to those of the connected inner conductors.

3. In combination, a pair of concentric transmission line sections having a common outer tubular conductor and each having an inner conductor separated from the outer conductor by a tubular insulator, an electric discharge device in end-to-end relationship with the inner conductors and said tubular insulators and comprising a tubular dielectric envelope and a pair of axially spaced electrodes sealed to ends of said dielectric envelope, the diameters of said electrodes being substantially equal to the diameters of the associated inner conductors and the outside diameter of said envelope being equal to the outside diameter of the tubular insulators, and means for controlling the density of the electrical discharge-- established between said electrodes for controlling the coupling between said pair of transmission line sections.

MILAN D. FISKE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 781,002 Hewitt Jan. 31, 1905 1,927,755 Rogowski Sept. 19, 1933 1,950,003 Hund Mar. 6, 1934 1,967,008 Hund July 17, 1934 1,984,499 St. Laurent Dec. 18, 1934 2,032,620 Langmuir Mar. 3, 1936 2,034,756 Hansell Mar. 24, 1936 2,106,770 Southworth et a1. Feb. 1, 1938 2,153,728 Southworth Apr. 11, 1939 2,170,050 Gandtner Aug. 22, 1939 2,308,523 Llwellyn Jan. 19, 1943 2,368,031 Llwellyn Jan. 23, 1945 

